Creating CustomItem in Java ME
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==Overview== | ==Overview== | ||
| − | This code snippet demonstrates how to create and display custom control. It consist of | + | This code snippet demonstrates how to create and display custom control. It consist of two files: |
| − | 1. CustomControl.java - | + | 1. CustomControl.java - Inherited from <tt>MIDlet</tt>, displays the MyItem control. |
| − | 2. MyItem.java | + | 2. MyItem.java - Inherited from <tt>CustomItem</tt>. |
| − | Custom contol class <tt>MyItem</tt> implements method <tt>keyPressed()</tt>,which is responsible for storing last key pressed code. | + | Custom contol class <tt>MyItem</tt> implements the method <tt>keyPressed()</tt>, which is responsible for storing the last key-pressed code. |
| − | + | It also implements the paint() method, which displays the last key-pressed code inside the control. | |
| Line 193: | Line 193: | ||
==Postconditions== | ==Postconditions== | ||
| − | After starting MIDlet, user will see custom control with | + | After starting the MIDlet, the user will see custom control with th elast key-pressed code. |
==Supplementary material== | ==Supplementary material== | ||
| − | You can | + | You can view the source file and executable application in the attached zip archive. The archive is available for download at [[Media:Creating_custom_control_in_J2ME.zip]] |
Related articles: | Related articles: | ||
Revision as of 16:16, 31 December 2008
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Article
Overview
This code snippet demonstrates how to create and display custom control. It consist of two files:
1. CustomControl.java - Inherited from MIDlet, displays the MyItem control.
2. MyItem.java - Inherited from CustomItem.
Custom contol class MyItem implements the method keyPressed(), which is responsible for storing the last key-pressed code. It also implements the paint() method, which displays the last key-pressed code inside the control.
Source file: CustomControl.java
import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.Form;
import javax.microedition.midlet.MIDlet;
public class CustomControl extends MIDlet implements CommandListener{
//Main form.
private Form form;
private Display display;
private Command exitCommand;
private MyItem myItem;
/**
* Constructor. Constructs the object and initializes displayables.
*/
public CustomControl() {
form = new Form("Custom Control MIDlet.");
// Add command buttons
exitCommand = new Command("Exit", Command.EXIT, 1);
form.addCommand(exitCommand);
form.setCommandListener(this);
display = Display.getDisplay(this);
display.setCurrent(form);
myItem = new MyItem("Custom control");
form.append(myItem);
}
/**
* From CommandListener.
* Called by the system to indicate that a command has been invoked on a
* particular displayable.
* @param cmd the command that was invoked
* @param displayable the displayable where the command was invoked
*/
public void commandAction(Command cmd, Displayable displayable) {
if (cmd == exitCommand) {
notifyDestroyed();
}
}
/**
* From MIDlet.
* Called when the MIDlet is started.
*/
public void startApp() {
// No implementation required.
}
/**
* From MIDlet.
* Called to signal the MIDlet to enter the Paused state.
*/
public void pauseApp() {
// No implementation required.
}
/**
* From MIDlet.
* Called to signal the MIDlet to terminate.
* @param unconditional whether the MIDlet has to be unconditionally
* terminated
*/
public void destroyApp(boolean unconditional) {
// No implementation required.
}
}
Source file: MyItem.java
import javax.microedition.lcdui.CustomItem;
import javax.microedition.lcdui.Font;
import javax.microedition.lcdui.Graphics;
class MyItem extends CustomItem {
// Last key pressed code.
private int key;
/**
* Constructor.
*/
public MyItem( String label ){
super( "" );
}
/**
* From CustomItem.
* Called by the system to redraw canvas.
* @param graphics used for drawing operations.
*/
public void paint(Graphics g, int width, int height) {
//Display last key pressed.
String output = "Key code:"+String.valueOf(key);
g.drawString(output,(width-g.getFont().stringWidth(output))/2,
(height-g.getFont().getHeight())/2, 0);
g.setStrokeStyle(Graphics.DOTTED);
for (int i= 0;i<(height+width)/10;i++)
{
g.setColor(i*10000);
g.drawRect( 0+i, 0+i, (width-i*2), (height-i*2));
}
}
/**
* From CustomItem.
* Called by the system to retrieve minimum width required for this control.
*/
protected int getMinContentWidth() {
return 150;
}
/**
* From CustomItem.
* Called by the system to retrieve minimum height required for this control.
*/
protected int getMinContentHeight() {
return 100;
}
/**
* From CustomItem.
* Called by the system to retrieve preferred width for this control.
*/
protected int getPrefContentWidth(int arg0) {
return 200;
}
/**
* From CustomItem.
* Called by the system to retrieve preferred height for this control.
*/
protected int getPrefContentHeight(int arg0) {
return 100;
}
/**
* From CustomItem.
* Called by the system to redraw canvas.
* @param graphics used for drawing operations.
*/
protected void keyPressed(int keyCode) {
key = keyCode;
this.repaint();
}
}
Postconditions
After starting the MIDlet, the user will see custom control with th elast key-pressed code.
Supplementary material
You can view the source file and executable application in the attached zip archive. The archive is available for download at Media:Creating_custom_control_in_J2ME.zip
Related articles: http://wiki.forum.nokia.com/index.php/KIJ000744_-_LCDUI:_CustomItem_content_remains_blank_when_appended_to_a_Form_before_setting_the_Form_as_current_Displayable

